With an aging population, rates of dementia will only climb, yet doctors have few effective strategies for addressing the worst symptoms.

Mild cognitive impairment, in which older adults show lapses in memory and other mental functions that aren’t serious enough to impair their daily activities, affects about 10% to 20% of those over age 70. Each year, about 10% of these people will progress to develop dementia, a more serious form of impairment that can drastically affect their independence and ability to function. But despite the growing proportion of the population that may be affected by these conditions, an analysis published in the Canadian Medical Association Journal found that there are few effective options for treating the condition.

The researchers reviewed 32 randomized controlled trials, in which patients were randomly assigned to either an intervention such as drugs to control cognitive decline, herbal remedies, physical activity or mental exercises including crossword puzzles; or left to continue living their lives without any changes. By comparing the various methods of treating cognitive decline, the scientists hoped to come up with some ranking of how effective the various interventions were.

They did not find strong evidence to support medications such as donepezil, a cholinesterase inhibitor designed to help brain chemicals keep neural circuits involved in cognition active. Studies have long hinted that such prescription drugs are only minimally effective in staving off the symptoms of dementia, but with so few medications to treat dementia available, many physicians continue to prescribe the medications since they can help some patients to improve recall.

There was also little evidence supporting the effectiveness of natural remedies such as the herbal supplement ginkgo, the hormone dehydroepiandrosterone (DHEA), or vitamin B and omega-3 fatty acids. The majority of the studies found these remedies had little to no effect on improving scores on memory tests or other evaluations of cognitive functions.

Studies investigating the role of estrogen and testosterone therapy showed the hormone therapies may actually increase risk of cognitive decline; among more than 10,000 women, those taking estrogen therapy increased their risk of dementia after five years by 80% compared to the women not taking the hormone, and studies of men taking testosterone suggested that the hormone might hamper short term memory.

Because recent studies hinted that physical activity could improve cognitive function in the elderly, the researchers also evaluated trials that included resistance and balance training as well as aerobic activities and found that resistance training improved short and long term memory of some participants, while aerobic activities helped some executive functions such as planning and organizing, but not memory. Overall, the researchers write, “There is some evidence that physical exercise may have a positive benefit, and given its countless other medical benefits, it should be encouraged with all patients.”

By far the intervention that showed the most dramatic benefits among healthy elderly adults involved mental exercise. These trials involved participants learning computer-based training programs or performing memory, reasoning and speed-processing exercises. Those who were trained on these types of skills showed significantly better memory and attention skills than those who did not, and one trial even reported that participants retained improved memory at a five year follow-up.

What are the best ways to engage the brain to reap these benefits? Anything that keeps thinking and organizational or memory circuits active can be helpful, according to recent studies. For example, last year, researchers from Tohoku University in Japan showed that elderly men and women could improve some of their declining mental abilities — at least in the short-term — by playing the game Brain Age, which quizzes users on a variety of topics and presents the queries in brain-teasing ways.

While it certainly can’t hurt to keep the brain active into old age, the researchers point out that it’s not clear whether intervening with crossword puzzles or daily sudoku can actually bypass mild cognitive impairment or steer an aging brain away from dementia. They note that many of the studies they evaluated involved a relatively small number of participants. But, the findings highlight the lack of effective strategies for addressing the growing prevalence of cognitive decline and dementia in the aging population. “Future studies should address the impact of cognitive training on the prevention of cognitive decline, and we encourage researchers to consider easily accessible tools such as crosswords puzzles and sudoku that have not been rigorously studied,” the authors conclude.